Active matrix type liquid crystal display apparatus

ABSTRACT

An active matrix type liquid crystal display apparatus, including a pair of substrates and a liquid crystal layer interposed between said pair of substrates. One of the pair of substrates has plural scanning electrodes and plural signal electrodes arranged to cross the plural scanning electrodes. Pixels are formed at regions surrounded by the scanning electrodes and the signal electrodes. Respective ones of the pixels include an active element arranged at a vicinity of the crossing point of the scanning electrode and the signal electrode, a pixel electrode connected to the active element and a common electrode arranged in correspondence to the pixel electrode. Further, there is provided a colored filter and a shielding layer having a specific resistivity of less than 10 8  Ω.cm.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/139,117, filedAug. 24, 1998, now U.S. Pat. No. 6,100,956, which is a continuation ofU.S. application Ser. No. 08/731,162, filed Oct. 10, 1996, now U.S. Pat.No. 5,805,247, the subject matter of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display apparatus,wherein an electric field is supplied in a direction parallel to thesurface of the substrate, and more particularly to an active matrix typeliquid crystal display apparatus which provides a wide viewing anglecompatible with a high image quality.

In a conventional liquid crystal display apparatus, an electrode fordriving a liquid crystal is formed on the surface of each of twosubstrates, respectively, so that the electrodes are facing each otheracross the liquid crystal. The above conventional liquid crystal displayapparatus uses a method which is represented by a twisted nematicdisplay mode, wherein the liquid crystal is driven by supplying anelectric field in a vertical direction with respect to the twosubstrates. In such case, transparent electrodes, such as ITO (IndiumTin Oxide), are used.

On the other hand, another mode of operation, wherein the liquid crystalis driven by supplying an electric field in a direction approximatelyparallel to the substrate using comb shaped electrodes provided on onesubstrate, is disclosed in JP-B-63-21907 (1988), and U.S. Pat. No.4,345,249. In this case, the electrodes need not necessarily betransparent, and opaque metallic electrodes having a high electricconductivity can be used.

However, in the display mode wherein the electric field is supplied tothe liquid crystal in a direction approximately parallel to thesubstrate using active elements (hereinafter called an in-planeswitching mode), any method to supply an adequate electric field to theliquid crystal without causing interference between the electric fieldssupplied in a direction parallel to the substrate in a condition where alarge amount of wiring exists, and any means to concurrently improve theimage quality, have not been disclosed entirely.

Generally speaking, in the in-plane switching mode, the electric fieldsinterfere with each other, because a large amount of wiring is formed ononly one of the substrates through which electric signals aretransmitted. Accordingly, the electric field supplied to the liquidcrystal is influenced by unnecessary electric fields, and so an adequateelectric field can not be supplied to the liquid crystal.

Furthermore, an unnecessary electric capacitance is formed between theelectrodes, which sometimes causes the voltage supplied to the liquidcrystal to fluctuate. The above described phenomena will causedeterioration of the image quality of the liquid crystal displayapparatus. Especially, an electric field generated by an image signalelectrode for transmitting signals to respective pixels having an activeelement, such as a TFT and the like, influences the electric fieldbetween a pixel electrode for operating the liquid crystal and thecommon electrode.

The potential of the image signal electrode varies always during theframe period in the course of transmitting signals. It has been knownthat, if the pixel electrode (its potential is in a floating conditionwhen the active element is in an off condition) is located close to theimage signal electrode, a nonuniformity appearing like shadow stripesreferred to as a smear, similar to a cross talking phenomenon, isgenerated in parallel with the image signal electrode depending on thevarying potential of the image signal electrode. In order to suppressthis phenomenon, a technique to arrange the common electrode, which isalways supplied with a potential from an external source, as the closestelectrode to the image signal electrode has been developed by thepresent inventor (U.S. patent application Ser. No. 08/374,531).

However, in accordance with the above technique, the shielding effectfor the electric field is not necessarily sufficient, and the problemcaused by generation of the smear phenomenon still exists. Although thesmear phenomenon could be suppressed by increasing the shielding effectwith broadening of the width of the common electrode, the broadening ofthe width of the common electrode causes another problem in which theaperture ratio of the liquid crystal display apparatus is decreased.

SUMMARY OF THE INVENTION

One of the objects of the present invention is to solve the aboveproblems, and to provide an active matrix type liquid crystal displayapparatus of the in-plane switching mode type, which is capable ofproviding a wide viewing angle and a high image quality withoutgenerating the smear phenomenon.

The gist of the present invention to achieve the above object is asfollows.

An active matrix type liquid crystal display apparatus, comprises aplurality of electrodes, which are formed on a substrate so that anelectric field in parallel to the substrate can be supplied to a liquidcrystal layer, and a polarizer is provided, which changes its opticalcharacteristics based on an alignment condition of the liquid crystallayer, wherein a shielding layer formed on the substrate in parallel tothe image signal electrodes has a specific resistivity of less than 10⁸Ω.cm.

The shielding layer formed on the substrate in parallel to the imagesignal electrodes is desirably further coated with an insulator of atleast 10⁸ Ω.cm.

The specific resistivity of the shielding layer formed in parallel tothe scanning electrode is also desirably at least 10⁸ Ω.cm.

A counterpart to an image signal electrode of the shielding layer formedin parallel to the image signal electrodes is preferably an electricconductor, and the potential of the shielding layer formed in parallelto the image signal electrodes is preferably set at the same level asthe potential of the common electrode.

This means that a member for absorbing an electric field is used as theshielding layer concurrently, so that the electric field generated fromthe image signal electrode is shielded so as to exert no influence onthe electric field supplied to the liquid crystal layer. Further, themember for absorbing the electric field may be arranged at only acounterpart to the image signal electrode, and a high shielding effectis generated by arranging the shielding layer made of a high insulatingmaterial, such as a metal, so as to cover the member.

The member for absorbing the electric field can be made of an electricconductor, such as a metal. In this case, the shielding effect for theelectric field can be increased by arranging the member for absorbingthe electric field at only the counterpart to the image signalelectrode, providing the member so as to have the same potential as thepotential of the common electrodes, and arranging the shielding layerhaving a high specific resistivity so that it covers the member.

As the insulating and shielding layer, an organic polymer material mixedwith conductive particles, such as metallic particles and/or carbonparticles, is used, and its specific conductivity can be controlled byadjusting the mixing amount of the conductive particles.

A theory of operation of the in-plane switching mode will be explainedhereinafter.

FIG. 1 indicates a schematic structure of an active matrix type liquidcrystal display apparatus of the in-plane switching mode type, relatingto the present invention. A feature is that the composition of the blackmatrix 22 a, which is parallel to the image signal electrodes, differsfrom the composition of the black matrix 22 b which is parallel to thescanning electrodes.

FIGS. 2(a) and 2(b) are schematic vertical cross sections indicating theoperation of the liquid crystal in the liquid crystal panel of thepresent invention, and FIGS. 2(c) and 2(d) are their schematicelevations. A vertical cross section of the cell when no voltage issupplied is indicated in FIG. 2(a), and its elevation is indicated inFIG. 2(c). Active elements are omitted in these figures. In accordancewith the present invention, plural pixels are formed by forming pluralstripe shaped electrodes, but only a part of the pixels are shown inFIGS. 2(a) and 2(b).

FIG. 3 indicates a relationship between an angle φ_(p) formed by thepolarized transmission axis 11 of the polarizer 8 to the direction ofthe electric field 9, and an angle φ_(LP) formed by the longitudinalaxis (an optical axis) of the liquid crystal molecule (the rubbingdirection 10) at the vicinity of the substrate boundary to the directionof the electric field 9. The polarizer and the substrate form a pair atthe upper region and lower region, respectively. Therefore, ifnecessary, the symbols φ_(P1), φ_(P2), φ_(LC1), φ_(LC2) are used.

As shown in FIG. 2(a), stripe shaped electrodes 1, 3, 4 are formedinside of a pair of transparent substrates 7, 7′, whereon alignmentlayers 5, 5′, are formed, and a liquid crystal layer is interposedbetween them.

A rod shaped liquid crystal molecule 6 is aligned so as to form an angleto the longitudinal direction of the stripe shaped electrodes 1, 4, thatis, 45 degrees <|φ_(LC)|≦90 degrees, when no voltage is supplied. In thefollowing explanation, a case when the alignment directions 10 of theliquid crystal molecules 6 at the upper boundary and the lower boundaryare in parallel, that is when φ_(LC1)=φ_(LC2), is taken as an example.The dielectric anisotropy of the liquid crystal composition is assumedto be positive, but, even if it is negative, no problem results.

By supplying an electric field 9, the liquid crystal molecules changetheir alignment direction along the direction of the electric field, asshown in FIGS. 2(b) and 2(d). Therefore, the optical transmissivity canbe altered by supplying an electric field while arranging the polarizers8, 8′ at a designated angle (direction of the polarized transmissionaxis 11).

When the dielectric anisotropy of the liquid crystal composition isnegative, the initial alignment direction is oriented to an angle|φ_(LC)|, which is perpendicular to the longitudinal direction of thestripe shaped electrode, (that is, 0 degree <|φ_(LC)|≦45 degrees).

A means for shielding unnecessary electric fields relating to thepresent invention will be explained hereinafter.

Smear, a cross talk phenomenon, can be decreased by restricting thespecific resistivity of the black matrix 22 a, which is in parallel tothe image signal electrodes, to less than 10⁸ Ω.cm.

In accordance with the in-plane switching mode, the electrodes areformed fundamentally only on the substrate whereon the active elementsare mounted. And, because the electric field is supplied in a directionparallel to the substrate, any conductor on the opposing substratebecomes a disturbance to the electric field.

Therefore, when a black matrix is provided on the opposing substrate, aninsulator, not a metal, which does not influence the supplied electricfield, has been used as the material for the black matrix.

The inventor found that the shielding effect, which ensured that theunnecessary electric field between the image signal electrodes 3 and thepixel electrodes, and between the pixel electrodes and the commonelectrodes 1, would not influence the electric field parallel to thesubstrate between the pixel electrodes and the common electrodes 1,could be obtained by restricting the specific resistivity of the blackmatrix formed in parallel to the image signal electrode 3 to less than10⁸ Ω.cm. The above finding is based on a relationship that an insulatorhaving a specific resistivity less than 10⁸ Ω.cm absorbs an electricfield even though it is an insulator.

The relationship is shown in FIG. 4(a). The relationship indicates adriving voltage at a spot (b), where the influence of the black matrixcould be expected, when the black matrix is formed on the substrate (II)counter to the substrate (I) having comb-shaped electrodes thereon, asshown in FIG. 4(b).

As a result, it was revealed that the driving voltage increased in arange wherein the specific resistivity of the black matrix material wasless than 10⁸ Ω.cm. This means that an insulator having a specificresistivity less than 10⁸ Ω.cm could absorb an electric field.Accordingly, a shielding effect with respect to the electric field,which is generated by the image signal electrodes and is unnecessary fordriving the liquid crystal layer, can be obtained by using an insulatorhaving a specific resistivity less than 10⁸ Ω.cm as the material for theblack matrix. And, an improvement in preventing the generation of crosstalk, appearing as a smear generated in parallel to the image signalelectrodes, can be achieved.

However, there are several practical methods-in setting the specificresistivity to less than 10⁸ Ω.cm for the black matrix formed counter tothe image signal electrodes in order to shield unnecessary electricfields of the image signal for preventing generation of cross talk Oneof the methods is that the entire black matrix formed counter to theimage signal electrodes is fabricated with a material having a specificresistivity which is less than 10⁸ Ω.cm. However, in this case, thepossibility exists that a displacement in alignment of the upper andlower substrates may occur, causing the black matrix to intrude into aliquid crystal driving region. In such a case, a problem may occur inthat an adequate electric field can not be supplied to the liquidcrystal layer. The problem relating to the alignment can be solved bymaking only a part of the black matrix formed counter to the imagesignal electrodes, especially only the part aligned with the imagesignal electrodes, have a specific resistivity less than 10⁸ Ω.cm, andproviding the rest of the part with material having a specificresistivity at least 10⁸ Ω.cm. The above double structure can bereplaced with a structure wherein the entire structure made of amaterial having a specific resistivity less than 10⁸ Ω.cm is coveredwith a material having a specific resistivity of at least 10⁸ Ω.cm, asshown in FIG. 7. Further, a structure wherein the material having aspecific resistivity less than 10⁸ Ω.cm may be interposed between thematerial having a specific resistivity of at least 10⁸ Ω.cm, as shown inFIG. 8. Furthermore, a structure wherein a concave shaped materialhaving a specific resistivity less than 10⁸ Ω.cm may be fit in a convexshaped material having a specific resistivity at least 10⁸ Ω.cm.

The shielding effect with respect to the electric field of the blackmatrix formed in parallel to the image signal electrodes can beincreased further by using an electrically conductive material as thematerial having a specific resistivity less than 10⁸ Ω.cm.

In the above case, the absorbing effect with respect to the electricfield can be more properly stabilized when the conductor has a constantpotential, than in a case when the conductor has a drifting potential.Accordingly, the shielding effect with respect to the electric field canbe increased further by setting the potential of the conductor always atthe same level as the potential of the common electrode 1.

The specific resistivity of the above materials, wherein metallicparticles or carbon are dispersed in an organic high polymer material,can be adjusted by controlling the amount of metallic particles orcarbon in the material.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will be understood more clearly from the following detaileddescription with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of an active matrix type liquidcrystal display apparatus relating to the present invention;

FIGS. 2(a), 2(b), 2(c), and 2(d) are schematic illustrations indicatingan operation of liquid crystals in an in-plane switching mode relatingto the present invention;

FIG. 3 is an illustration indicating definitions of a rubbing directionand an axial direction of a polarizer;

FIG. 4(a) is a graph indicating the influence of specific resistivity ofa black matrix to an electric field supplied to liquid crystals, FIG.4(b) is a schematic illustration of the substrate used in an experimentfor obtaining the result shown in FIG. 4(a), and FIG. 4(c) is a crosssection taken along line A-A′ in FIG. 4(b);

FIG. 5 is a plan view of a typical example of an electrode structure ina unit pixel of a liquid crystal display apparatus relating to thepresent invention, FIG. 5(A) is a section view taken along line A-A′ andFIG. 5(B) is a section taken along line B-B′ in FIG. 5;

FIG. 6 is a schematic view representing an example of a structure of acolor filter substrate, FIG. 6(A) is a section view taken along lineA-A′ and FIG. 6(B) is a section view taken along line B-B′ in FIG. 6;

FIG. 7 is a schematic view representing another example of a structureof a color filter substrate, FIG. 7(A) is a section view taken alongline A-A′ and FIG. 7(B) is a section view taken along line B-B′ in FIG.7, and FIG. 7(C) is an enlargement of the area C in FIG. 7;

FIG. 8 is a schematic view representing another example of a structureof a color filter substrate, FIG. 8(A) is a section view taken alongline A-A′ and FIG. 8(B) is a section view taken along line B-B′ in FIG.8, and FIG. 8(C) is an enlargement of the area C in FIG. 8;

FIG. 9 is a schematic circuit diagram of a liquid crystal displayapparatus relating to the present invention; and

FIG. 10 is a wave form diagram indicating an example of wave forms whena common electrode is made to operate as an alternating currentelectrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, various embodiments of the present invention will beexplained with reference to the drawings.

Embodiment 1

FIG. 1 is a schematic diagram of an active matrix type liquid crystaldisplay apparatus relating to the present invention, and FIG. 5illustrates the structures of the thin film transistor (referred tohereinafter as a TFT) and respective electrodes in a unit pixel of theabove panel display.

In accordance with the present invention, as also seen in FIG. 2(a), theactive matrix type liquid crystal display apparatus comprises a pair ofsubstrates 7, 7′, a liquid crystal layer formed by liquid crystalmolecules 6 interposed between the substrates, plural scanningelectrodes 12, plural image signal electrodes 3 which cross the pluralscanning electrodes 12 to form a matrix shape, pixel electrodes 4 formedclosely and in parallel to the image signal electrodes 3, and plural TFT14, which are active elements, formed at points where the scanningelectrodes 12 cross the image signal electrodes and the pixel electrodes4, all of the above electrodes and the TFT being formed on the onesubstrate 7 of the pair of substrates. An insulating layer, i.e. asilicon nitride layer, is formed on the above members, and additionallyan alignment layer 5 is applied onto the insulating layer. The alignmentlayer 5, which is composed of an organic composition, is provided at aboundary between the substrate 7 and the liquid crystal layer, andrubbing treatment is performed on the surface of the alignment layer.

Common electrodes 1 are formed between the pixel electrodes 4 andadjacent image signal electrodes 3 so as to generate an electric field 9in parallel to the substrate between the pixel electrodes 4 and thecommon electrodes 1 formed in the active elements, as shown in FIG.2(b).

In accordance with the present embodiment, color filters 23 with a blackmatrix were formed on the other one of the substrates, as shown in FIG.1, polyimide was applied onto the surface of the color filters andrubbing treatment was performed thereon.

A plan view from a direction perpendicular to the substrate is shown inFIG. 5 and schematic cross sectional views taken on the lines A—A, andB-B′ in the plan view of a typical example of the electrode structureare shown in FIG. 5(A) and FIG. 5(B), respectively.

The TFT 14 is composed of pixel electrodes (source electrodes) 4, imagesignal electrodes (drain electrodes) 3, scanning electrodes (gateelectrodes) 12, and amorphous silicon 13. The common electrodes 1, thescanning electrodes 12, the image signal electrodes 3, and the pixelelectrodes 4 were formed from the same metallic layer by making apattern.

Capacitance elements 16 were formed by a structure, wherein theinsulating layer 2 was interposed between the pixel electrode 4 and thecommon electrode 1 in a region between the two common electrodes 1, andanother insulating layer 25 was also interposed between the alignmentlayer 5 and the pixel electrode 4, as shown in the A-A′ cross sectionalview in FIG. 5(A).

The pixel electrodes 4 are arranged among three common electrodes 1, asshown in the plan view of FIG. 5. The pixel pitch is laterally, i.e.between the image signal electrodes 3, 100 μm, and longitudinally, i.e.between the scanning electrodes 12, 300 μm. The width of the scanningelectrode 12 which extends across plural pixels, and the portions of theimage signal electrode 3 and the common electrode 1 extending inparallel to the scanning electrode 12 (the horizontal direction in FIG.5), were formed to be wide in order to avoid any defect in wiring. Theabove widths are, respectively, 10 μm, 8 μm, and 8 μm.

On the contrary, the portions of the pixel electrode 4 and the commonelectrode 1 extending in parallel to the longitudinal direction of theimage signal electrode 3, which portion were formed independently by arespective unit pixel, were formed to be somewhat narrow, such as 5 μmand 6 μm, respectively. The narrow width of the electrode provides anincreased possibility of a short or breakage of the circuit bycontamination with dust or the like, but the defect is restricted toonly a unit pixel, so that the defect is not likely to be extended to aline defect.

An interval of 2 μm was provided between the image signal electrode 3and the common electrode 1 using an insulating layer.

A schematic illustration of an example of the color filter substratecomposition with a black matrix is shown in FIG. 6. FIG. 6 is a planview as seen from a direction perpendicular to the substrate andschematic cross sectional views taken on lines A-A′ and B-B′ in the planview are shown in FIG. 5 and FIGS. 6(A) and 6(B), respectively.

A material prepared by mixing carbon and organic pigments was used asthe material for the black matrix. The black matrix arranged in parallelto the scanning electrode 12 was formed by the steps of applying theblack matrix material (a) onto the substrate, exposing a pattern, anddeveloping the pattern. Subsequently, the black matrix arranged inparallel to the image signal electrode 3 was formed by the steps ofapplying the black matrix material (b) onto the substrate, exposing apattern, and developing the pattern. Width of the black matrix was 16μm, and it was formed so not to enter into the pixel region from acenter line through the width of the common electrode 1. The arrangementof the black matrix on the electrodes substrate is indicated as a windowexpressed by dashed lines in FIG. 5. The specific resistivities of theblack matrix materials (a) and (b) were adjusted by controlling themixed amounts of carbon. In the present embodiment, the specificresistivity of the material (a) was 2×10⁹ Ω.cm, and that of the material(b) was 8×10⁷ Ω.cm (both values were the specific resistivities afterforming the black matrix, hereinafter the same specific resistivity wasused).

Subsequently, an active matrix type liquid crystal display apparatusrelating to the present invention was obtained by forming the colorfilter 23 at respective regions R, G, and B by the steps of coating withphotosensitive resins mixed with pigments, exposing a pattern, anddeveloping.

Embodiment 2

The present embodiment is the same as the embodiment 1 except for thefollowing items.

The specific resistivity of the material (a) for the black matrix, whichwas arranged in parallel to the scanning electrode 12, was changed to1×10⁸ Ω.cm. And, the specific resistivity of the material (b) for theblack matrix, which was arranged in parallel to the image signalelectrode 3, was changed to 5×10⁷ Ω.cm.

Embodiment 3

The present embodiment is the same as the embodiment 1 except for thefollowing items.

A schematic illustration of another example of the color filtersubstrate composition with a black matrix is shown in FIG. 7. The blackmatrix, which was arranged in parallel to the image signal electrode 3,was formed with the material (b). The width of the black matrix wassomewhat narrower than that of the image signal electrode 3, i.e. 6 μm.Then, the black matrix, which was arranged in parallel to the scanningelectrode 12, and a coating surrounding both sides of the black matrixformed with the material (b), were formed with the material (a).

The final width of the black matrix in parallel to the image signalelectrode 3 was 16 μm. The arrangement of the black matrix in theelectrode substrate is indicated as a window expressed by the dashedlines in FIG. 5.

In the present embodiment, the specific resistivity of the material (a)for the black matrix was 3×10¹⁰ Ω.cm, and of the material (b) for theblack matrix was 3×10⁶ Ω.cm.

Embodiment 4

The present embodiment is the same as the embodiment 1 except for thefollowing items.

A schematic illustration of another example of the color filtersubstrate composition with a black matrix is shown in FIG. 8. The blackmatrix, which was arranged in parallel to the image signal electrode 3,was formed with the material (b). The width of the black matrix wassomewhat narrower than that of the image signal electrode 3, i.e. 6 μm.Then, the black matrix, which was arranged in parallel to the scanningelectrode 12, and a coating surrounding both sides of the black matrixformed with the material (b), were formed with the material (a).

The final width of the black matrix in parallel to the image signalelectrode 3 was 16 μm. The arrangement of the black matrix in theelectrode substrate is indicated as a window expressed by the dashedlines in FIG. 5.

In the present embodiment, the specific resistivity of the material (a)for the black matrix was 5×10⁹ Ω.cm, and of the material (b) for theblack matrix was 5×10⁶ Ω.cm.

Embodiment 5

The present embodiment is the same as the embodiment 3 except for thefollowing items.

The black matrix, which was arranged in parallel to the image signalelectrode 3, was formed using chromium as the material (b). The width ofthe black matrix was somewhat narrower than the image signal electrode3, i.e. 6 μm.

Further, the black matrix made of chromium was coated with the material(a). The final width of the black matrix in parallel to the image signalelectrode 3 was 16 μm. Simultaneously, the black matrix in parallel tothe scanning electrode 12 was formed. The arrangement of the blackmatrix in the electrode substrate is indicated as a window expressed bythe dashed lines in FIG. 5.

In the present embodiment, the specific resistivity of the material (a)for the black matrix was 1×10¹⁰ Ω.cm.

Embodiment 6

In the present embodiment, the active matrix type liquid crystal displayapparatus obtained in the embodiment 5 was used.

In order to supply an alternating current to the common electrode 1, thefollowing arrangement was adopted. An image signal electrode drivingcircuit 18 was connected to the respective image signal electrodes 3,and a scanning electrode driving circuit 19 was connected to therespective scanning electrodes 12, as indicated in FIG. 9. A commonelectrode driving circuit 20 was connected to the common electrode 1.All of the above driving circuits were controlled by a control circuit17.

A signal having information is supplied to the image signal electrode 3,and a scanning signal is supplied to the scanning electrode 12synchronously with the information signal. The information signal istransmitted from the image signal electrode 3 to the pixel electrode 4via the TFT 14, and a voltage is supplied to the liquid crystal layerbetween the liquid crystal layer and the common electrode 1. Inaccordance with the present embodiment, a voltage wave form is alsosupplied to the common electrode 1, and a higher voltage by as much asthe voltage supplied to the common electrode 1 is supplied to the liquidcrystal layer. The supplied wave forms to respective wiring electrodesare indicated in FIG. 10.

The amplitudes of the voltage wave forms were set as follows:

V_(D-CENTER)=14.0

V_(GH)=28.0

V_(GL)=0

V_(DH)=16.4

V_(DL)=11.4

V_(CH)=15.1

V_(CL)=9.1

In this case, the metallic portion of the black matrix in parallel tothe image signal electrode 3 was connected to the common electrode 1 soas to have always the same potential as the common electrode 1.

The active matrix type liquid crystal display apparatus, wherein thevoltage to the common electrode 1 was supplied by an alternatingcurrent, had a wide viewing angle, which did not cause any reversion ofthe gradation in a range of 60 degrees in all four directions, i.e.right, left, up, and down, and no smear, resulting from cross talkgenerated along the image signal electrode 3, was observed.

In accordance with the present invention, an active matrix type liquidcrystal display apparatus of the in-plane switching mode type, having awide viewing angle and no cross talk generation can be obtained bymaking the shielding layer (black matrix), which is formed in parallelto the image signal electrodes in the in-plane switching mode, have thespecific resistivity of, at the utmost, 10⁸ Ω.cm.

Furthermore, an active matrix type liquid crystal display apparatus ofthe in-plane switching mode type, generating no cross talk, can beobtained by coating the black matrix with an insulating layer having thespecific resistivity of at least 10⁸ Ω.cm.

What is claimed is:
 1. An active matrix type liquid crystal displayapparatus, comprising: a pair of opposed substrates; and a liquidcrystal layer interposed between said pair of substrates; one of saidpair of substrates comprising (a) plural scanning electrodes, (b) pluralimage signal electrodes crossing said plural scanning electrodes, (c)plural active elements formed at respective crossing points of saidplural scanning electrodes and said plural image signal electrodes, (d)plural pixel electrodes formed on said plural active elements, and (e)plural common electrodes for generating an electric field between saidpixel electrodes and common electrodes; wherein a shielding layer isprovided between another of said pair of substrates and said pluralimage signal electrodes at least at a part of an upper region on saidplural image signal electrodes, and a specific resistivity of at least apart of said shielding layer is less than 10⁸ Ω.cm; wherein at leastsaid part of said shielding layer is composed of a material having aspecific resistivity of less than 10⁸ Ω.cm; and wherein at least saidpart of said shielding layer composed of said material having a specificresistivity of less than 10⁸ Ω.cm has a width narrower than a width ofsaid image signal electrodes.